Cerebral perfusion correlates of depressed mood

The Legacy of the TTASAAN Report-Premature Conclusions and Forgotten Promises: A Review of Policy and Practice Part I

Brain perfusion single photon emission computed tomography (SPECT) scans were initially developed in 1970's. A key radiopharmaceutical, hexamethylpropyleneamine oxime (HMPAO), was originally approved in 1988, but was unstable. As a result, the quality of SPECT images varied greatly based on technique until 1993, when a method of stabilizing HMPAO was developed. In addition, most SPECT perfusion studies pre-1996 were performed on single-head gamma cameras. In 1996, the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (TTASAAN) issued a report regarding the use of SPECT in the evaluation of neurological disorders. Although the TTASAAN report was published in January 1996, it was approved for publication in October 1994. Consequently, the reported brain SPECT studies relied upon to derive the conclusions of the TTASAAN report largely pre-date the introduction of stabilized HMPAO. While only 12% of the studies on traumatic brain injury (TBI) in the TTASAAN report utilized stable tracers and multi-head cameras, 69 subsequent studies with more than 23,000 subjects describe the utility of perfusion SPECT scans in the evaluation of TBI. Similarly, dementia SPECT imaging has improved. Modern SPECT utilizing multi-headed gamma cameras and quantitative analysis has a sensitivity of 86% and a specificity of 89% for the diagnosis of mild to moderate Alzheimer's disease-comparable to fluorodeoxyglucose positron emission tomography. Advances also have occurred in seizure neuroimaging. Lastly, developments in SPECT imaging of neurotoxicity and neuropsychiatric disorders have been striking. At the 25-year anniversary of the publication of the TTASAAN report, it is time to re-examine the utility of perfusion SPECT brain imaging. Herein, we review studies cited by the TTASAAN report vs. current brain SPECT imaging research literature for the major indications addressed in the report, as well as for emerging indications. In Part II, we elaborate technical aspects of SPECT neuroimaging and discuss scan interpretation for the clinician.

Effects of acute mild hypoxia on cerebral blood flow in pilots

BACKGROUND

Pilots often face and need to overcome a diverse range of unfavorable conditions, of which hypoxic exposure is the most common. Studies have reported that hypoxia can induce a decrease in cerebral blood flow (CBF) in the brains of both humans and animals. Hypoxia and the associated cerebral hemodynamic changes can contribute to cognitive performance deficits that may endanger flight safety and increase the risk of accidents.

AIM

In this study, we aimed to identify region-specific alterations in CBF in male pilots after exposure to hypoxia.

MATERIAL AND METHODS

We used 3D pseudo-continuous arterial spin labeling sequences in 35 healthy male pilots (mean age: 30.6 ± 4.82 years) under simulated hypoxic conditions with a 3.0-T magnetic resonance imaging scanner. The generated CBF maps were measured and averaged in several regions of interest.

RESULTS

Hypoxia decreased CBF in various brain regions, including the right temporal and bilateral occipital lobes, the anterior and posterior lobes of the cerebellum, the culmen and declive, and the inferior semilunar lobule of the cerebellum.

CONCLUSION

These changes may impact the functional activity of the brains of pilots experiencing hypoxia in flight, but the related mechanisms require further investigation.

Multimodal Magnetic Resonance Imaging and Therapeutic Intervention With Yi-nao-jie-yu Decoction in a Rat Model of Post-stroke Depression

Post-stroke depression (PSD) is the most common neuropsychiatric complication after a stroke, though its neuropathological characteristics have not been fully elucidated. Comprehensive and non-invasive magnetic resonance (MR) assessment techniques are urgently needed for current research, as diffusion tensor imaging (DTI), arterial spin labeling (ASL), and magnetic resonance spectroscopy (MRS) can allow for a comprehensive assessment of neuropathological changes in the brain. These techniques can provide information about microscopic tissue integrity, cerebral perfusion, and cerebral metabolism, and can serve as powerful tools for investigating neurophysiological changes associated with PSD. Yi-nao-jie-yu decoction (YNJYD) is a Chinese herbal formulation based on the theory of traditional Chinese medicine, with demonstrated clinical efficacy in the treatment of PSD. The aim of this study was to use these MR techniques to evaluate changes in PSD and YNJYD-treated rats. This is the first experimental study in animals to investigate neuropathological changes associated with PSD using a combination of multiple MR techniques, including DTI, ASL, and MRS. In addition, we investigated the effect of YNJYD in a rat model of PSD by assessing changes in brain tissue microstructure, brain metabolism, and cerebral perfusion. First, depressive-like behaviors of PSD rats were assessed by the open field test (OFT), sucrose preference test (SPT), and Morris water maze (MWM) test, and then the integrity of the rats' microstructure was assessed by DTI, the levels of regional cerebral perfusion were assessed by ASL, and changes in the relative concentrations of brain metabolites were determined by MRS. The results showed that OFT and SPT scores were significantly reduced in PSD rats, as was performance in the MWM; these PSD-associated changes were attenuated in rats administered YNJYD, with improved depressive-like behaviors evidenced by increased OFT and SPT scores and improved performance in the MWM task. Furthermore, we found that PSD rats had lower perfusion levels in the prefrontal cortex (PFC) and hippocampus (HP), microstructural damage, and abnormal changes in the concentrations of brain metabolites; YNJYD exerted therapeutic effects on PSD rats by improving microcirculation in the PFC and HP, regulating glutamatergic systems and membrane phospholipid metabolism, and repairing microstructural damage.

Ketogenic diet enhances neurovascular function with altered gut microbiome in young healthy mice

Neurovascular integrity, including cerebral blood flow (CBF) and blood-brain barrier (BBB) function, plays a major role in determining cognitive capability. Recent studies suggest that neurovascular integrity could be regulated by the gut microbiome. The purpose of the study was to identify if ketogenic diet (KD) intervention would alter gut microbiome and enhance neurovascular functions, and thus reduce risk for neurodegeneration in young healthy mice (12–14 weeks old). Here we show that with 16 weeks of KD, mice had significant increases in CBF and P-glycoprotein transports on BBB to facilitate clearance of amyloid-beta, a hallmark of Alzheimer’s disease (AD). These neurovascular enhancements were associated with reduced mechanistic target of rapamycin (mTOR) and increased endothelial nitric oxide synthase (eNOS) protein expressions. KD also increased the relative abundance of putatively beneficial gut microbiota (Akkermansia muciniphila and Lactobacillus), and reduced that of putatively pro-inflammatory taxa (Desulfovibrio and Turicibacter). We also observed that KD reduced blood glucose levels and body weight, and increased blood ketone levels, which might be associated with gut microbiome alteration. Our findings suggest that KD intervention started in the early stage may enhance brain vascular function, increase beneficial gut microbiota, improve metabolic profile, and reduce risk for AD.

Classification of Depression, Cognitive Disorders, and Co-Morbid Depression and Cognitive Disorders with Perfusion SPECT Neuroimaging

BACKGROUND

Depression and cognitive disorders (CDs) are two common co-morbid afflictions that commonly present with overlapping symptoms.

OBJECTIVE

To evaluate if perfusion neuroimaging with brain SPECT can distinguish persons with depression from those with CDs or both conditions.

METHODS

Inclusion criteria were DSM-IV defined depression or CDs (Alzheimer's disease, vascular dementia, dementia not otherwise specified, and amnestic disorders not otherwise specified) including persons with both (total n = 4,541; 847 CDs, 3,269 depression, 425 with both). Perfusion differences between the groups were calculated using two-sampled t-tests corrected for multiple comparisons. Diagnostic separation was determined with discriminant analysis. Feature selection revealed predictive regions in delineating depression from CDs and comorbid cases.

RESULTS

Persons with CDs had lower cerebral perfusion compared to depression. In co-morbid persons, cerebral hypoperfusion was additive, with regions showing lower regional cerebral blood flow compared to either diagnosis alone. Both baseline and concentration SPECT regions yielded correct classification of 86% and leave one out cross-validation of 83%. AUC analysis for SPECT regions showed 86% accuracy, 80% sensitivity and 75% specificity. Discriminant analysis separated depression and CDs from comorbid cases with correct classification of 90.8% and cross validated accuracy of 88.6%. Area under the curve was 83% with sensitivity of 80% and specificity of 70%. Feature selection identified the most predictive regions in left hippocampus, right insula, cerebellar, and frontal lobe regions.

CONCLUSION

Quantitative perfusion SPECT neuroimaging distinguishes depression from dementia and those with both co-morbidities. Perfusion brain SPECT can be utilized clinically to delineate between these two disorders.

Caloric restriction preserves memory and reduces anxiety of aging mice with early enhancement of neurovascular functions

Neurovascular integrity plays an important role in protecting cognitive and mental health in aging. Lifestyle interventions that sustain neurovascular integrity may thus be critical on preserving brain functions in aging and reducing the risk for age-related neurodegenerative disorders. Here we show that caloric restriction (CR) had an early effect on neurovascular enhancements, and played a critical role in preserving vascular, cognitive and mental health in aging. In particular, we found that CR significantly enhanced cerebral blood flow (CBF) and blood-brain barrier function in young mice at 5-6 months of age. The neurovascular enhancements were associated with reduced mammalian target of rapamycin expression, elevated endothelial nitric oxide synthase signaling, and increased ketone bodies utilization. With age, CR decelerated the rate of decline in CBF. The preserved CBF in hippocampus and frontal cortex were highly correlated with preserved memory and learning, and reduced anxiety, of the aging mice treated with CR (18-20 months of age). Our results suggest that dietary intervention started in the early stage (e.g., young adults) may benefit cognitive and mental reserve in aging. Understanding nutritional effects on neurovascular functions may have profound implications in human brain aging and age-related neurodegenerative disorders.

Age Drives Distortion of Brain Metabolic, Vascular and Cognitive Functions, and the Gut Microbiome

Advancing age is the top risk factor for the development of neurodegenerative disorders, including Alzheimer's disease (AD). However, the contribution of aging processes to AD etiology remains unclear. Emerging evidence shows that reduced brain metabolic and vascular functions occur decades before the onset of cognitive impairments, and these reductions are highly associated with low-grade, chronic inflammation developed in the brain over time. Interestingly, recent findings suggest that the gut microbiota may also play a critical role in modulating immune responses in the brain via the brain-gut axis. In this study, our goal was to identify associations between deleterious changes in brain metabolism, cerebral blood flow (CBF), gut microbiome and cognition in aging, and potential implications for AD development. We conducted our study with a group of young mice (5-6 months of age) and compared those to old mice (18-20 months of age) by utilizing metabolic profiling, neuroimaging, gut microbiome analysis, behavioral assessments and biochemical assays. We found that compared to young mice, old mice had significantly increased levels of numerous amino acids and fatty acids that are highly associated with inflammation and AD biomarkers. In the gut microbiome analyses, we found that old mice had increased Firmicutes/Bacteroidetes ratio and alpha diversity. We also found impaired blood-brain barrier (BBB) function and reduced CBF as well as compromised learning and memory and increased anxiety, clinical symptoms often seen in AD patients, in old mice. Our study suggests that the aging process involves deleterious changes in brain metabolic, vascular and cognitive functions, and gut microbiome structure and diversity, all which may lead to inflammation and thus increase the risk for AD. Future studies conducting comprehensive and integrative characterization of brain aging, including crosstalk with peripheral systems and factors, will be necessary to define the mechanisms underlying the shift from normal aging to pathological processes in the etiology of AD.

A Comparison of Neuroimaging Abnormalities in Multiple Sclerosis, Major Depression and Chronic Fatigue Syndrome (Myalgic Encephalomyelitis): is There a Common Cause?

There is copious evidence of abnormalities in resting-state functional network connectivity states, grey and white matter pathology and impaired cerebral perfusion in patients afforded a diagnosis of multiple sclerosis, major depression or chronic fatigue syndrome (CFS) (myalgic encephalomyelitis). Systemic inflammation may well be a major element explaining such findings. Inter-patient and inter-illness variations in neuroimaging findings may arise at least in part from regional genetic, epigenetic and environmental variations in the functions of microglia and astrocytes. Regional differences in neuronal resistance to oxidative and inflammatory insults and in the performance of antioxidant defences in the central nervous system may also play a role. Importantly, replicated experimental findings suggest that the use of high-resolution SPECT imaging may have the capacity to differentiate patients afforded a diagnosis of CFS from those with a diagnosis of depression. Further research involving this form of neuroimaging appears warranted in an attempt to overcome the problem of aetiologically heterogeneous cohorts which probably explain conflicting findings produced by investigative teams active in this field. However, the ionising radiation and relative lack of sensitivity involved probably preclude its use as a routine diagnostic tool.

Neuroimaging Biomarkers of Caloric Restriction on Brain Metabolic and Vascular Functions

PURPOSE OF REVIEW

Non-invasive neuroimaging methods have been developed as powerful tools for identifying in vivo brain functions for studies in humans and animals. Here we review the imaging biomarkers that are being used to determine the changes within brain metabolic and vascular functions induced by caloric restriction (CR), and their potential usefulness for future studies with dietary interventions in humans.

RECENT FINDINGS

CR causes an early shift in brain metabolism of glucose to ketone bodies, and enhances ATP production, neuronal activity and cerebral blood flow (CBF). With age, CR preserves mitochondrial activity, neurotransmission, CBF, and spatial memory. CR also reduces anxiety in aging mice. Neuroimaging studies in humans show that CR restores abnormal brain activity in the amygdala of women with obesity and enhances brain connectivity in old adults.

SUMMARY

Neuroimaging methods have excellent translational values and can be widely applied in future studies to identify dietary effects on brain functions in humans.

Changes in the regional cerebral blood flow detected by arterial spin labeling after 6-week escitalopram treatment for major depressive disorder

BACKGROUND

A few studies have used pseudo-continuous arterial spin labeling (pCASL) to assess the regional cerebral blood flow (rCBF) in patients with major depressive disorder (MDD). However, rCBF changes during treatment with escitalopram have not been studied in detail. We used pCASL to investigate the effect of 6-week escitalopram treatment on the rCBF in MDD patients.

METHODS

We subjected 53 MDD patients and 36 controls to pCASL (T1, baseline). The patients then received treatment with escitalopram for 6 weeks and 27 were scanned again (T2). We used selected regions of interest that exhibited differences between the controls and patients at T1 and compared the T2 rCBF in the patients with the T1 rCBF of the controls. We also compared the T1 and T2 rCBF in the patients to assess their response to escitalopram.

RESULTS

After 6-week treatment with escitalopram, the rCBF in the patients' left inferior temporal gyri, the middle- and inferior frontal gyri, and the subgenual anterior cingulate, which had been higher at T1 than in the controls, was decreased. Their rCBF in the right lingual gyrus remained significantly lower at T2.

LIMITATION

We did not have a placebo-control group and the number of patients available at T2 was small.

CONCLUSION

In MDD patients, 6-week escitalopram treatment elicited significant rCBF changes toward normalization in most of the areas that had shown significant differences between the patients and the controls at T1. The persistence of rCBF anomalies in the right lingual gyrus may be a trait marker of MDD.

Cerebrovascular perfusion among older adults is moderated by strength training and gender

Cerebral perfusion is important in older adults as it is linked to cognitive declines. Physical activity can improve blood flow in the body but little is known about the relationship between physical activity and cerebral perfusion in older adults. In particular, no study has investigated the relation between strength training and cerebral perfusion. We examined whether different types of physical activity (assessed with the Rapid Assessment of Physical Activity questionnaire) were associated with MRI cerebrovascular perfusion in 59 older adults. There was a significant interaction between gender and strength training, such that women who engaged in strength training (weight lifting or calisthenics) at least once per week exhibited significantly greater cerebrovascular perfusion than women who did not. This interaction remained significant after controlling for other physical activity, demographics, and health variables. These findings suggest that regular strength training can be beneficial for cerebrovascular health in women.

Quantification of Tc-99m-ethyl cysteinate dimer brain single photon emission computed tomography images using statistical probabilistic brain atlas in depressive end-stage renal disease patients: Correlation with disease severity and symptom factors

This study adapted a statistical probabilistic anatomical map of the brain for single photon emission computed tomography images of depressive end-stage renal disease patients. This research aimed to investigate the relationship between symptom clusters, disease severity, and cerebral blood flow. Twenty-seven patients (16 males, 11 females) with stages 4 and 5 end-stage renal disease were enrolled, along with 25 healthy controls. All patients underwent depressive mood assessment and brain single photon emission computed tomography. The statistical probabilistic anatomical map images were used to calculate the brain single photon emission computed tomography counts. Asymmetric index was acquired and Pearson correlation analysis was performed to analyze the correlation between symptom factors, severity, and regional cerebral blood flow. The depression factors of the Hamilton Depression Rating Scale showed a negative correlation with cerebral blood flow in the left amygdale. The insomnia factor showed negative correlations with cerebral blood flow in the left amygdala, right superior frontal gyrus, right middle frontal gyrus, and left middle frontal gyrus. The anxiety factor showed a positive correlation with cerebral glucose metabolism in the cerebellar vermis and a negative correlation with cerebral glucose metabolism in the left globus pallidus, right inferior frontal gyrus, both temporal poles, and left parahippocampus. The overall depression severity (total scores of Hamilton Depression Rating Scale) was negatively correlated with the statistical probabilistic anatomical map results in the left amygdala and right inferior frontal gyrus. In conclusion, our results demonstrated that the disease severity and extent of cerebral blood flow quantified by a probabilistic brain atlas was related to various brain areas in terms of the overall severity and symptom factors in end-stage renal disease patients.

Neural correlates of memory in depression measured by brain perfusion SPECT at rest

AIM

Brain metabolism activated studies have indicated associations between memory and the anterior cingulate cortex and hippocampus in patients with depression. The aim of the present study was therefore to investigate memory function, measured as performance on the Wechsler Memory Scale-Revised (WMS-R), and its relationship to brain perfusion using single-photon emission computed tomography (SPECT) at rest in patients with depression.

METHODS

The Hamilton Rating Scale for Depression (HAMD) and WMS-R were measured for 17 patients with depression by an independent clinical evaluation team. Voxel-based correlation analyses were performed with statistical parametric mapping at an extent threshold of 200 voxels. Associations were controlled for state and trait factors.

RESULTS

WMS-R measurements of verbal, visual, and general memory were inversely correlated with brain perfusion in the right anterior cingulate cortex, left premotor cortices, and both regions, respectively. The HAMD directly correlated with brain perfusion in the right anterior cingulate cortex.

CONCLUSION

Brain perfusion SPECT measurements of the anterior cingulate cortex at rest were associated with the severity of depression and immediate memory scores measured with the WMS-R.

The functional neuroanatomy of geriatric depression

OBJECTIVE

Positron Emission Tomography (PET) studies of cerebral glucose metabolism have demonstrated sensitivity in evaluating the functional neuroanatomy of treatment response variability in depression, as well as in the early detection of functional changes associated with incipient cognitive decline. The evaluation of cerebral glucose metabolism in late life depression may have implications for understanding treatment response variability, as well as evaluating the neurobiological basis of depression in late life as a risk factor for dementia.

METHODS

Sixteen patients with geriatric depression and 13 comparison subjects underwent resting PET studies of cerebral glucose metabolism, as well as magnetic resonance (MR) imaging scans to evaluate brain structure.

RESULTS

Cerebral glucose metabolism was elevated in geriatric depressed patients relative to comparison subjects in anterior (right and left superior frontal gyrus) and posterior (precuneus, inferior parietal lobule) cortical regions. Cerebral atrophy (increased cerebrospinal fluid [CSF] and decreased grey and white matter volumes) were observed in some of these regions, as well. Regional cerebral metabolism was positively correlated with severity of depression and anxiety symptoms.

CONCLUSIONS

In contrast to decreased metabolism observed in normal aging and neurodegenerative conditions such as Alzheimer's disease, cortical glucose metabolism was increased in geriatric depressed patients relative to demographically matched controls, particularly in brain regions in which cerebral atrophy was observed, which may represent a compensatory response.

Depressive disorders: focally altered cerebral perfusion measured with arterial spin-labeling MR imaging

PURPOSE

To assess focal cerebral perfusion in patients with refractory depressive disorder (RDD), patients with nonrefractory depressive disorder (NDD), and healthy control subjects by using arterial spin-labeling (ASL) magnetic resonance (MR) imaging.

MATERIALS AND METHODS

This study was approved by the local ethical committee, and written informed consent was obtained from all participants. Twenty-four patients with RDD, 37 patients with NDD, and 42 healthy control subjects were included. From February 2006 to July 2007, all participants were imaged with a 3-T MR system. ASL and echo-planar images were subtracted and averaged to give perfusion-weighted images. Voxel-based analysis was performed. Region-of-interest analysis was applied to the bilateral hippocampi, thalami, and lentiform nuclei.

RESULTS

Patients with NDD showed reduced perfusion in the left prefrontal cortex versus control subjects and increased perfusion mainly in the limbic-striatal areas (P < .05). In contrast, patients with RDD had decreased perfusion predominantly in the bilateral frontal and bilateral thalamic regions (P < .05). Compared with patients with RDD, patients with NDD showed higher perfusion mainly in the limbic-striatal areas (P < .05). In region-of-interest analysis, the NDD group showed higher regional cerebral blood flow than both RDD and control groups in the left hippocampus (P = .045), right hippocampus (P = .001), and right lentiform nucleus (P = .049).

CONCLUSION

This study revealed alterations of regional perfusion in the brains of patients with RDD that differed from those in patients with NDD. These results are consistent with the concept that RDD is associated with decreased activity of the bilateral prefrontal areas; and NDD, with decreased activity of left frontal areas in conjunction with overactivity of the bilateral limbic system.

Prefrontal cortical functional abnormality in major depressive disorder: a stereotactic meta-analysis

OBJECTIVE

First, the objective was to test the hypothesis that prefrontal cortical regions most often reported to be maximally abnormal in studies of major depressive disorder, correspond to those regions reported maximally active when healthy subjects engage in diverse emotional tasks. Second, the objective was to determine whether such regions are reported typically to be either over or under-active.

METHOD

Medline and Embase were used to search for neuroimaging studies of major depressive disorder from 1990 to 2005. Forty-two original studies using voxel based techniques were included, and compared with data from our previous meta-analysis on healthy subjects which included one hundred and eighty-one original studies [Steele, J.D., Lawrie, S.M., 2004b. Segregation of cognitive and emotional function in the prefrontal cortex: a stereotactic meta-analysis. Neuroimage 21, 868-875].

RESULTS

The medial prefrontal cortex is the region reported maximally abnormal most often when healthy subjects experience emotion. The region is centred on Broadmans Area (BA) 32 but extends into BA 25. Two further clusters of reported loci were identified in the lateral prefrontal cortex: one in the lateral orbitofrontal region reported active when healthy subjects experience emotion (BA 47); the other centred on a dorsolateral region (BA 46 and 9) associated with cognitive tasks. No reporting bias for overactivity or underactivity was identified.

LIMITATIONS

This study pooled data from diverse studies deliberately. There were insufficient numbers of original studies to support sub-group analyses.

CONCLUSIONS

Despite the variability of reports in the literature, activity reported to be abnormal in depressive disorder is particularly localised to those brain regions that represent the substrate for normal emotional experience in healthy subjects.

Prefrontal hyperactivation during working memory task in untreated individuals with major depressive disorder

The prefrontal cortex, a part of the limbic-thalamic-cortical network, participates in regulation of mood, cognition and behavior and has been implicated in the pathophysiology of major depressive disorder (MDD). Many neuropsychological studies demonstrate impairment of working memory in patients with MDD. However, there are few functional neuroimaging studies of MDD patients during working memory processing, and most of the available ones included medicated patients or patients with both MDD and bipolar disorder. We used functional magnetic resonance imaging (fMRI) to measure prefrontal cortex function during working memory processing in untreated depressed patients with MDD. Fifteen untreated individuals with Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition recurrent MDD (mean age+/-s.d.=34.3+/-11.5 years) and 15 healthy comparison subjects (37.7+/-12.1 years) matched for age, sex and race were studied using a GE/Elscint 2T MR system. An echo-planar MRI sequence was used to acquire 24 axial slices. The n-back task (0-back, 1-back and 2-back) was used to elicit frontal cortex activation. Data were analyzed with a multiple regression analysis using the FSL-FEAT software. MDD patients showed significantly greater left dorsolateral cortex activation during the n-back task compared to the healthy controls (P<0.01), although task performance was similar in the two groups. Furthermore, the patients showed significant anterior cingulate cortex activation during the task, but the comparison subjects did not (P<0.01). This study provides in vivo imaging evidence of abnormal frontolimbic circuit function during working memory processing in individuals with MDD.

Relationship between regional cerebral blood flow and separate symptom clusters of major depression: A single photon emission computed tomography study using statistical parametric mapping

This study examined the relationship between resting regional cerebral blood flow (rCBF) patterns in patients with major depressive disorder (MDD) and specific symptom clusters derived from ratings on the Hamilton Rating Scale for Depression (HRSD) and the Mini Mental State Examination. We hypothesized that the functional activity in frontal, parietal, anterior cingulate, basal ganglia and limbic regions would be related to specific symptom domains. Fifteen patients fulfilling DSM-IV criteria for MDD who were off all psychotropic medications for >4 weeks and 15 normal volunteers were recruited. Single photon emission computed tomography (SPECT) images were obtained after (99m)Tc-ECD injection, and correlations between rCBF patterns and symptom severity ratings were calculated on a voxel-by-voxel basis, using statistical parametric mapping (SPM). Severity of depressive mood was inversely correlated with rCBF in the left amygdala, lentiform nucleus, and parahippocampal gyrus, and directly correlated with rCBF in the right postero-lateral parietal cortex (p < 0.001, uncorrected for multiple comparisons). Insomnia severity was inversely correlated with rCBF in the right rostral and subgenual anterior cingulate cortices, insula and claustrum. Anxiety severity was directly correlated with rCBF in the right antero-lateral orbitofrontal cortex, while cognitive performance was directly correlated with rCBF in the right postero-medial orbitofrontal cortex and in the left lentiform nucleus. Our findings confirmed the prediction that separate symptom domains of the MDD syndrome are related to specific rCBF patterns, and extend results from prior studies that suggested the involvement of anterior cingulate, frontal, limbic and basal ganglia regions in the pathophysiology of MDD.

Mechanisms of action underlying the effect of repetitive transcranial magnetic stimulation on mood: behavioral and brain imaging studies

In a set of experiments, we applied 10-Hz repetitive transcranial magnetic stimulation (rTMS) over the left mid-dorsolateral frontal cortex (MDLFC) to investigate rTMS-induced changes in affective state and neural activity in healthy volunteers. In Experiment 1, we combined 10-Hz rTMS with a speech task to examine rTMS-induced changes in paralinguistic aspects of speech production, an affect-relevant behavior strongly linked to the ACC. In Experiment 2, we combined 10-Hz rTMS with positron emission tomography (PET) and used partial least squares (PLS) to identify a pattern of brain regions whose connectivity with the site of stimulation varied as a function of rTMS. The results of Experiment 1 revealed that following stimulation of the left MDLFC, subjects reported having less positive affect and vitality and displayed more monotonous speech. In Experiment 2, results revealed that 10-Hz rTMS influenced the covariation between blood flow at the site of stimulation (ie the left MDLFC) and blood flow in a number of affect-relevant brain regions including the perigenual anterior cingulate gyrus, insula, thalamus, parahippocampal gyrus, and caudate nucleus. Taken together, our results suggest that changes in affect and affect-relevant behaviour following 10-Hz rTMS applied over the left MDLFC may be related to changes in neural activity in brain regions widely implicated in affective states, including a frontocingulate circuit.

Correlation between cerebral blood flow and items of the Hamilton Rating Scale for Depression in antidepressant-naive patients

BACKGROUND

The purpose of this study was to correlate the basal cerebral blood flow (CBF) in patients with major depressive disorder (MDD) with the score for each of the 21 questions in the Hamilton Rating Scale for Depression (HRSD), in order to determine the cerebral regions associated with each item.

METHODS

Fourteen antidepressant-naive patients with unipolar depression (DSM-IV criteria for MDD) participated in this study with a HRSD score of >/=20 points. CBF images obtained by SPECT were analyzed by SPM99 software. The significant correlation threshold for a priori regions (frontocortical and limbic regions) was a Z value of at least 2.25 and clusters formed by more than 10 voxels.

RESULTS

Items 1, 6, 11 and 20 were positively correlated with right medial frontal gyrus; item 7 was negatively correlated with bilateral medial frontal gyrus. Items 2 and 10 were positively correlated with right anterior and medial cingulate, respectively. Item 5 was negatively correlated with the left amygdala. Item 9 was negatively correlated with bilateral insula, and item 16 with right insula. Items 12 and 14 were positively correlated with right and left precentral frontal gyrus, respectively.

LIMITATIONS

The small sample size and only out-patients included in the study.

CONCLUSIONS

The frontal cortex plays an important role in the expression of MDD symptoms. Not all the symptoms evaluated correlated with one single structure, which may explain the diverse results reported in the literature. These preliminary results support the necessity of further analyses by symptoms that could provide more specific information on the pathophysiology of MDD.

Audioverbal cognitive dysfunction in depression. Factors involved

There is increasing evidence suggesting that depression is associated with a certain degree of cognitive dysfunction. However, there is still debate on whether this dysfunction is only substantially associated with the most severe forms of depression, on whether or not it decreases in parallel with clinical response, and on the role played in these changes by psychotropic medications. In order to clarify these questions, we analyzed the performance in several cognitive tasks that involved attention and working memory of 40 untreated subjects with a diagnosis of dysthymia or major depressive disorder without melancholia. The protocol used included three audioverbal tasks: vocal reaction time (VRT), inverse spelling (IS) and text repetition (TR). The protocol was also administered to 20 healthy volunteers that were used as a comparison group. The same battery of assessments was administered 2 months later to all 60 subjects. At the time of the second assessment, patients (but not healthy volunteers) were on antidepressant medication, in accordance with common clinical practice. The authors found a longer VRT in patients versus healthy volunteers at baseline. VRT did not decrease in patients that responded to treatment. However, there was an improvement in VRT in patients that took sertraline (n=16) compared to subjects taking imipramine (n=11). This fact was not attributable to differences in antidepressant response. Performance in the two other tasks was globally worse in the patient group than in the comparison group, and there was also an absence of improvement in the scores of patients who responded to treatment. However, when the sample was stratified by illness duration, individuals with less than 10 years from the first episode of depression showed a decrease in IS errors compared to the healthy volunteers. It is concluded that patients with nonmelancholic depression suffer from cognitive dysfunction, that this dysfunction persists after clinical improvement and that at least attention is influenced by the type of medication taken. Time from onset of the disorder also seems to influence changes in cognitive performance.

Left dorso-lateral repetitive transcranial magnetic stimulation affects cortical excitability and functional connectivity, but does not impair cognition in major depression

PURPOSE

Transcranial magnetic stimulation (TMS) has been used for over a decade to investigate cortical function. More recently, it has been employed to treat conditions such as major depression. This study was designed to explore the effects of differential treatment parameters, such as stimulation frequency. In addition, the data were examined to determine whether a change in connectivity occurred following TMS.

METHOD

Fifteen patients with major depression were entered into a combined imaging and treatment experiment with single photon emission computed tomography (SPECT) and repetitive transcranial magnetic stimulation (rTMS) over left dorso-lateral prefrontal cortex (DLPFC). Brain perfusion during a verbal fluency task was compared between pre- and poststimulation conditions. Patients were then treated with 80% of motor threshold for a total of 10 days, using 5000 stimuli at 5, 10 or 20 Hz. Tests of cortical excitability and neuropsychological tests were done throughout the trial.

FINDINGS

Patients generally improved with treatment. There was no perceptible difference between stimulation frequencies, which may have reflected low study power. An increase in rostral anterior cingulate activation after the treatment day was associated with increased functional connectivity in the dorso-lateral frontal loop on the left and the limbic loop on both sides. No noticeable deterioration in neuropsychological function was observed.

CONCLUSION

TMS at the stimulation frequencies used seems to be safe over a course of 5000 stimuli. It appears to have an activating effect in anterior limbic structures and increase functional connectivity in the neuroanatomical networks under the stimulation coil within an hour of stimulation.

Principal components of the Beck Depression Inventory and regional cerebral metabolism in unipolar and bipolar depression

BACKGROUND

We determined clustering of depressive symptoms in a combined group of unipolar and patients with bipolar disorder using Principle Components Analysis of the Beck Depression Inventory. Then, comparing unipolars and bipolars, these symptom clusters were examined for interrelationships, and for relationships to regional cerebral metabolism for glucose measured by positron emission tomography.

METHODS

[18F]-fluoro-deoxyglucose positron emission tomography scans and Beck Depression Inventory administered to 31 unipolars and 27 bipolars, all medication-free, mildly-to-severely depressed. BDI component and total scores were correlated with global cerebral metabolism for glucose, and voxel-by-voxel with cerebral metabolism for glucose corrected for multiple comparisons.

RESULTS

In both unipolars and bipolars, the psychomotor-anhedonia symptom cluster correlated with lower absolute metabolism in right insula, claustrum, anteroventral caudate/putamen, and temporal cortex, and with higher normalized metabolism in anterior cingulate. In unipolars, the negative cognitions cluster correlated with lower absolute metabolism bilaterally in frontal poles, and in right dorsolateral frontal cortex and supracallosal cingulate.

CONCLUSIONS

Psychomotor-anhedonia symptoms in unipolar and bipolar depression appear to have common, largely right-sided neural substrates, and these may be fundamental to the depressive syndrome in bipolars. In unipolars, but not bipolars, negative cognitions are associated with decreased frontal metabolism. Thus, different depressive symptom clusters may have different neural substrates in unipolars, but clusters and their substrates are convergent in bipolars.

Potential mechanisms of the sleep therapies for depression

Sleep deprivation for one night has been investigated as a treatment for depression since the first publications describing its antidepressant properties almost 30 years ago [Pflug and Tolle, 1971: Int Pharmacopsychiatry 6:187-196]. It remains a field of active research. It is the only intervention consistently demonstrated to produce next-day antidepressant results. This makes sleep deprivation an exciting and unique tool to study the pathophysiology of depressive disorders and to formulate targets for novel antidepressant agents. Importantly, it is also an effective, but underused, clinical treatment for unipolar and bipolar depression.

Event-Related Potentials and Cognitive Processing of Affectively Toned Words in Depression

Abstract Background: Depressed subjects and euthymic controls demonstrate differences in cognitive processing and brain electrophysiology. Contingent negative variation (CNV) and postimperative negative variation (PINV) was used to investigate the relationship between cognition and cortical event related potentials. Method: Electrophysiological responses and memory of different personality trait adjectives were measured in 15 patients with major depressive disorder and 15 euthymic controls. The words were presented acoustically to elicit event-related potentials. The subjects were asked to indicate whether the words were self-referential. Responses were measured separately for self referential and non-self referential, neutral, positively and negatively toned words. Results: Depressed patients chose more negative and fewer positive words as self-referential, though no significant differences between groups in CNV magnitude for any of the words were found. Persistence of cortical negativity after the motor response (PINV) was significantly (P < 0.02) greater in patients for all non-self-referential words, and reaction times were significantly longer for all words. Recall of positive words and recognition of all words were significantly impaired in patients. Conclusions: Both electrophysiological measures and memory tests found differences between depressed patients and controls, suggesting that the PINV wave may be a useful electrophysiological probe to clarify the neurophysiological basis of cognitive processes.

Regional cerebral blood flow changes in drug-resistant depressed patients following treatment with transcranial magnetic stimulation: a statistical parametric mapping analysis

Changes of regional cerebral blood flow (rCBF) in five drug-resistant depressed patients were examined by single photon emission computed tomography (SPECT) with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) before and after treatment with transcranial magnetic stimulation (TMS). The SPECT images were analysed with the Statistical Parametric Mapping (SPM) package. TMS administered in the region of the left dorsolateral prefrontal cortex (DLPFC) of the depressed patients was associated with an increase of rCBF at a focal region some distance from the stimulation site. No change was observed at any other remote region.

Assessing the performance of SPM analyses of spect neuroactivation studies. Statistical Parametric Mapping

Several simulations of SPECT neuroactivation studies have been performed in order to determine the influence of both study size and activation focus characteristics on the detection of brain activation foci following a pixel-based statistical analysis. This was achieved by developing a methodology based on the Hoffman software brain phantom, SPECT acquisition simulation software, standard reconstruction software, and the Statistical Parametric Mapping (SPM96) package. We present results on the minimal activation levels required for focus detection. Furthermore, the improved sensitivity of the analysis resulting from the use of an iterative reconstruction technique (OSEM) with regard to the classical filtered backprojection (FBP) is assessed quantitatively, and the various physical, processing, and physiological parameters that potentially influence the detection of foci are discussed. Finally, the influence is investigated of the height threshold as implemented in SPM96 upon the size of the detected foci. Practical guidelines are proposed with regard to the number of subjects per group for SPECT activation studies following the split-dose design.

Cerebral perfusion in chronic fatigue syndrome and depression

BACKGROUND

Patients with chronic fatigue syndrome (CFS) and depressive illness share many, but not all, features.

AIMS

To test the hypothesis that patients with CFS have abnormal cerebral perfusion, that differs from that in patients with depressive illness.

METHOD

We recruited 30 patients with CFS who were not depressed, 12 depressed patients and 15 healthy volunteers. Regional cerebral perfusion at rest was assessed using region of interest (ROI) and voxel-based statistical parametric mapping (SPM) techniques.

RESULTS

On SPM analysis there was increased perfusion in the right thalamus, pallidum and putamen in patients with CFS and in those with depressive illness. CFS patients also had increased perfusion in the left thalamus. Depressed patients differed from those with CFS in having relatively less perfusion of the left prefrontal cortex. The results were similar on ROI analysis.

CONCLUSIONS

Abnormal cerebral perfusion patterns in CFS subjects who are not depressed are similar but not identical to those in patients with depressive illness. Thalamic overactivity may be a correlate of increased attention to activity in CFS and depression; reduced prefrontal perfusion in depression may be associated with the greater neuropsychological deficits in that disorder.

Depressive illness

WHO estimate that by the beginning of the next century major unipolar depression will be one of the most important causes of ill health overall. Whereas the cause of depression is still obscure, it is becoming clear that a number of diverse factors are likely to be implicated, both genetic and environmental. Effective treatment of depression similarly involves a variety of methods, from electro-convulsive therapy to inter-personal psychotherapy. The pathophysiology of depression is gradually becoming accessible through research strategies, such as functional neuroimaging paired with mood altering interventions.

Prediction of antidepressant effects of sleep deprivation by metabolic rates in the ventral anterior cingulate and medial prefrontal cortex

OBJECTIVE

Sleep deprivation has been shown to have an antidepressant benefit in a subgroup of depressed patients. Functional imaging studies by the authors and others have suggested that patients with elevated metabolic rates in the anterior cingulate gyrus at baseline are more likely to respond to either sleep deprivation or antidepressant medications than patients with normal metabolic rates. The authors extend their earlier work in a larger group of patients and explore additional brain areas with statistical probability mapping.

METHOD

Thirty-six patients with unipolar depression and 26 normal volunteers were studied with positron emission tomography before and after sleep deprivation. Response to sleep deprivation was defined as a 40% or larger decrease in total scores on the Hamilton Depression Rating Scale.

RESULTS

One-third of the depressed patients had a significant response to sleep deprivation. Responders had higher relative metabolic rates in the medial prefrontal cortex, ventral anterior cingulate, and posterior subcallosal gyrus at baseline than depressed patients who did not respond to sleep deprivation and normal volunteers. Lower Hamilton depression scores correlated significantly with lower metabolic rates in the left medial prefrontal cortex. After sleep deprivation, significant decreases in metabolic rates occurred in the medial prefrontal cortex and frontal pole in the patients who responded positively to sleep deprivation.

CONCLUSIONS

High pretreatment metabolic rates and decreases in metabolic rates after treatment in the medial prefrontal cortex may characterize a subgroup of depressed patients who improve following sleep deprivation and, perhaps, other antidepressant treatments.

Effects of high amphetamine dose on mood and cerebral glucose metabolism in normal volunteers using positron emission tomography (PET)

The effects of high euphorigenic doses of D-amphetamine (0.9-1.0 mg/kg p.o.) on regional cerebral glucose metabolism (rCMRglu) and psychological measures were investigated in 10 healthy human volunteers using a within-subject design and [F-18]-fluorodeoxyglucose positron emission tomography (FDG-PET) and a variety of psychological assessments. At the dose tested, D-amphetamine produced a mania-like syndrome concomitantly with a widespread increase in absolute cerebral metabolism, which was significant in the anterior cingulate cortex, caudate nucleus, putamen, and thalamus. An exploratory analysis revealed that: (1) certain aspects of this mania-like syndrome correlated positively with the metabolic changes seen in the frontal cortex, caudate nucleus and putamen; and (2) some of the amphetamine-induced changes in CMRglu correlated with D-amphetamine plasma levels. The present findings of cortical and subcortical increases in cerebral metabolism after D-amphetamine application in humans accord with previous studies in animals, demonstrating that relatively high doses of D-amphetamine (presumably at least 1 mg/kg) are needed to increase cerebral glucose metabolism.

Regional cerebral blood flow and comorbid diagnosis in abstinent opioid addicts

Studies using single photon emission computed tomography (SPECT) have found low cerebral blood flow (CBF) in frontal and parietal cortices in patients with chronic opiate dependence. In the present study, SPECT with 99mTc-HMPAO as tracer was used to compare 27 detoxified opiate addicts with nine healthy control subjects. All the subjects were evaluated with clinical psychiatric (DSM-IV), psychometric and neuropsychological measures. Compared with normal control subjects, the addicts showed a non-significant reduction of whole brain perfusion values. Significant hypoperfusion in the right frontal and left temporal lobes was found in addicts with comorbid depression, and a significant decrease in CBF in the right frontal lobe was observed in those with antisocial tendencies. A significant negative correlation emerged between Depression subscale scores on the Minnesota Multiphasic Personality Inventory and left temporal CBF in the patients. No significant correlations were found, however, between measures of cognition and CBF in opiate addicts. The asymmetrical findings in CBF that characterized the addicts relative to normal control subjects may be more closely related to mood and behavioral traits than to substance abuse, per se.

Neuropsychological function and diurnal variation in depression

Twenty-six patients suffering from DSM-III-R major depressive episode with diurnal variation of mood were examined at approximately 8 AM and 8 PM, using a neuropsychological test battery. We found that tests of executive function, especially the verbal fluency test, were sensitive measures of diurnal variation, but that personality measures were relatively robust in that they were not significantly affected by diurnal variations of mood. The relevance of detecting and assessing diurnal changes of mood with reliable, objective measures of performance is discussed.